Hey, I fixed the O/D slip i originally had, by changing the filter and fluid (didnt drain the TC though) But...now I have a new problem

Right before I changed the fluid, I experienced a sort of, "Moan" in first gear, and sometimes in second. And after the fluid change, i still experience this moan in first and second under acceleration, and it will delay and sometime shift hard between 1st and second... All other gears are normal. It almost feels like something is locked up in the tranny.

Also, if i just dont punch the gas, and i go real slowly, i wont experience the moan or hard shift at all... It will shift normal.

Any insight? should i try changing the filter and fluid again after a couple hundred miles like I've seen other people say? I did not add the lucas additive like i was recommended yet...should I?

Thanks in advance!